It depends on what shape the other oil nipples are and what shape your oil gun is. If you get grease nipples which have a spring loaded end you can remove the spring and ball if that helps. You can try these no connection or maybe you have a local supplier.
Harrison Lubrication Engineering Ltd
Lynstock Way. Lostock. Bolton. Lancashire. BL6 4SA
Working Days: Monday – Friday
Working Hours: 8:30 – 17:00
Phone: 01204 691352
Email: sales@hle.co.uk
Website http://www.hle.co.uk
David